The monitoring for environmental contamination, including biological particles, is important in a number of industrial and commercial environments such as manufacturing facilities for pharmaceuticals, food and hospitals, and has also become important in public spaces such as airports, banks, postal handling facilities and government offices where there is concern for possible urban terrorist attacks.
In the pharmaceutical, healthcare and food industries a real time detector of environmental microbial levels is useful for public health, quality control and regulatory purposes. For example, parenteral drug manufacturers are required by the Food and Drug Administration to monitor the particulate and microbial levels in their aseptic clean rooms. Conventional microbiological methods require the collection of samples on growth media, and incubation at the correct temperature for the correct period of time (typically days). These methods assume that a viable microorganism is one that will undergo cellular division when placed in or on a growth media. For quantitative tests, growth is demonstrated by a visually detectable colony. There is a significant quantity of published literature that shows substantial limitations of using traditional culture and plate counting methods. For example, the published literature indicates variable results can be obtained depending upon the growth media used, the incubation time and temperature, and the condition of the microorganism prior to attempts to cultivate (e.g., slow growing, stressed, or sub-lethally damaged). Conventional methods also have no ability in real-time to locate probable sources of the contamination. In these applications, an instrument that can detect microbial particles, including bacteria, yeasts and molds, in the environment instantaneously and at low concentrations will be a useful tool and have significant advantages over conventional nutrient plate culture methods that require days for microbes to grow and be visually detected. It would also be useful to have an instrument that would be able to assist in locating, preferably in real-time, sources of particulate contamination.
There exist various prior art devices that employ particle size measurement and light induced fluorescence techniques as early warning sensors for bio-agents. Among these devices are fluorescence biological particle detection system of Ho (Jim Yew-Wah Ho, U.S. Pat. Nos. 5,701,012; 5,895,922; 6,831,279); FLAPS and UV-APS by TSI of Minnesota (Peter P. Hairston; and Frederick R. Quant; U.S. Pat. No. 5,999,250), and a fluorescence sensor by Silcott (U.S. Pat. No. 6,885,440). A proposed bio-sensor based on laser-induced fluorescence using a pulsed UV laser is described by T. H. Jeys, et al., Proc. IRIS Active Systems, vol. 1, p. 235, 1998. This is capable of detecting an aerosol concentration of five particles per liter of air, but involves expensive and delicate instruments. Other particle counters are manufactured by Met One Instrument, Inc. of Grants Pass, Oreg., Particle Measurement Systems, Inc., of Boulder, Colo., and Terra Universal Corp., of Anaheim, Calif.
Various detectors have been designed to detect airborne allergen particles and provide warning to sensitive individuals when the number of particles within an air sample exceeds a predetermined minimum value. Among these detectors are those described in U.S. Pat. Nos. 5,646,597, 5,969,622, 5,986,555, 6,008,729, 6,087,947, and 7,053,783, all to Hamburger et al. These detectors all involve direction of a light beam through a sample of environmental air such that part of the beam will be scattered by any particles in the air, a beam blocking device for transmitting only light scattered in a predetermined angular range corresponding to the predetermined allergen size range, and a detector for detecting the transmitted light.
Improved methods for the detection of airborne or liquidborne particles, particularly methods for distinguishing biologic and non-biologic particles in real-time, that would also assist in the identification the source of the particles are highly desirable. The real-time detection capability (total particle and microbe counts) is an enabling feature for implementing other real time monitoring devices, such as video camera, in order to have a more comprehensive surveillance and monitoring of area of interest. Such methods would allow for the determination of sources of contamination in controlled environments such as clean rooms, and provide improved methods for the control and prevention of contamination.